How do I assess muscle tone?

From the Guidelines

To assess muscle tone, perform a passive range of motion examination by moving the patient's relaxed limbs while they're in a comfortable position, as recommended by recent guidelines 1. This assessment is crucial in evaluating neurological conditions that may affect muscle tone. When performing the examination, begin by instructing the patient to relax completely, then gently move their joints through their full range of motion while noting any resistance. Normal tone feels like smooth, consistent minimal resistance throughout the movement. Abnormal findings include hypotonia (decreased resistance, floppy limbs), hypertonia (increased resistance), spasticity (velocity-dependent resistance that increases with faster movement), or rigidity (consistent resistance throughout the range). Some key points to consider during the assessment include:

• Compare sides for asymmetry, as this often indicates pathology
• The biceps, triceps, wrist flexors/extensors, quadriceps, and hamstrings are commonly assessed muscle groups
• Document your findings using descriptive terms rather than numerical scales, although scales like the Modified Ashworth scale can be used to quantify spasticity 1 This assessment is important because muscle tone abnormalities can indicate neurological conditions affecting upper motor neurons (causing spasticity), lower motor neurons or cerebellum (causing hypotonia), or extrapyramidal systems (causing rigidity), as noted in guidelines for stroke rehabilitation 1 and neurodevelopmental outcomes in children with congenital heart disease 1. Always perform this examination gently to prevent discomfort and ensure accurate results.

From the Research

Assessing Muscle Tone

To assess muscle tone, several methods can be employed, including:

• Palpation, a crucial skill for diagnosis, although it is not measurable objectively 2
• Objective methods, such as measuring biomechanical properties of the muscle, which have been developed to overcome the limitations of palpation 2
• Modified Ashworth Scale, a tool used to assess spastic hypertonia at the injected muscles 3, 4
• Ultrasonography, which can measure muscle echo intensity, providing valuable information on muscle tone 4
• Botulinum toxin assessment, which can help evaluate the effectiveness of treatment for cervical dystonia and other causes of hypertonia of the neck 5

Tools and Scales

Various tools and scales can be used to assess muscle tone, including:

• Modified Ashworth Scale, which has been used in several studies to evaluate the effectiveness of treatment for spasticity 3, 4
• Heckmatt scale, which categorizes patients into four groups based on muscle echo intensity 4
• Ultrasonography, which provides a non-invasive method for measuring muscle echo intensity 4

Clinical Applications

Assessing muscle tone is crucial in various clinical applications, including:

• Diagnosis and treatment of spasticity and dystonia 2, 3, 4, 5, 6
• Evaluation of the effectiveness of botulinum toxin therapy 3, 4, 5, 6
• Development of treatment algorithms and injection schemes for botulinum toxin therapy 6